Solve for $x$ and $y$ using substitution. ${-x+y = -7}$ ${y = -2x-4}$
Answer: Since $y$ has already been solved for, substitute $-2x-4$ for $y$ in the first equation. ${-x + }{(-2x-4)}{= -7}$ Simplify and solve for $x$ $-x-2x - 4 = -7$ $-3x-4 = -7$ $-3x-4{+4} = -7{+4}$ $-3x = -3$ $\dfrac{-3x}{{-3}} = \dfrac{-3}{{-3}}$ ${x = 1}$ Now that you know ${x = 1}$ , plug it back into $\thinspace {y = -2x-4}\thinspace$ to find $y$ ${y = -2}{(1)}{ - 4}$ $y = -2 - 4$ $y = -6$ You can also plug ${x = 1}$ into $\thinspace {-x+y = -7}\thinspace$ and get the same answer for $y$ : ${-}{(1)}{ + y = -7}$ ${y = -6}$